8.6  Presentation of assessments of risk of bias

A ‘Risk of bias’ table is available in RevMan for inclusion in a Cochrane review as part of the ‘Characteristics of included studies’ table. For each entry, the judgement (‘Low risk’ of bias; ‘High risk’ of bias, or ‘Unclear risk’ of bias) is followed by a text box for a description of the design, conduct or observations that underlie the judgement. Figure 8.6.a provides an example of how it might look. If the text box is left empty, and the judgement is left as ‘Unclear risk’, then the entry will be omitted from the ‘Risk of bias’ table for the study on publication in the CDSR.

 

Considerations for presentation of ‘Risk of bias’ assessments in the review text are discussed in Chapter 4 (Section 4.5) (under the Results subheading ‘Risk of bias in included studies’ and the Discussion subheading ‘Quality of the evidence’).

 

Two figures may be generated using RevMan for inclusion in a published review. First, a ‘Risk of bias graph’ figure illustrates the proportion of studies with each of the judgements (‘Low risk’, ‘High risk’, ‘Unclear risk’ of bias) for each entry in the tool (see Figure 8.6.b). Second, a ‘Risk of bias summary’ figure presents all of the judgements in a cross-tabulation of study by entry (see Figure 8.6.c).

 

An alternative, and perhaps preferable, version of the first figure (the ‘Risk of bias graph’) would be to restrict attention to studies in a particular important meta-analysis, and to represent the proportion of information (rather than the proportion of studies) at low risk, unclear risk and high risk of bias. The proportion of information may be measured by the sums of weights awarded to the studies in the meta-analysis. However, such plots cannot currently be produced within RevMan.